Gamma-ray spectroscopy of neutron-rich A~100nuclei

The shell model is one of the most well-known models for describing the structure of the nucleus. It is similar to the atomic shell model as protons and neutrons have their own independent shells which when filled offer greater stability for the nucleus by having a reduced binding energy per nucleon. These shells occur at specific numbers however have been shown to be different to atomic shell model for electrons. A problem with this model is that it makes calculating the binging energy per nucleon difficult as to do this the interaction between each of the nucleons must be calculated which becomes exceptionally difficult for heavy nuclei, thus other methods must be applied (National research council, 1999).
The Liquid drop model has been shown to be very accurate for predicting the binding energies of nucleons with very small error (Moller, et al., 1984). It compares the nucleus to a liquid droplet and how molecules in a liquid will interact with each other similar to the nucleons in a nucleus as both will have uniform density and exhibit similar characteristics when interacted with. Examples of this are that nuclear fission can be thought of as the splitting of a molecule, particle decay is similar to emission by evaporation and emission of radiation is similar to cooling (Brehm and Mullin, 1989).
These models, along with various others, have all added to our understanding of the structure of nuclei and have reproduced masses that have already been measured. However there are still a large number of nuclei that have not yet been measured experimentally, particularly for neutron rich nuclei and investigating these unknowns is essential to developing our knowledge of the nucleus.
There are various methods for investigating the mass of nuclei, one of which is the measurement of the time of flight through a magnetic spectrometer which can be used to find the mass as it is proportional to the change to mass ratio. An example of this is GANIL where nuclei of similar charge to mass ratios are accelerated within a cyclotron and as the lighter of the nuclei will accelerate faster than the lighter nuclei, there will be a delay in arrival at the detector. This time delay can then be used to calculate the charge to mass ratio of the nuclei to a high degree of accuracy (Chartier, 2002).